As for a liquid-level control valve of the fuel tank, there is one, as shown in FIG. 16, in which a valve member 101 engages the upper part of a float 100 so as to be relatively movable. Also, by a projection 100aformed in the middle of the upper part of this float 100, the valve member 101 is pushed upward, and the valve member 101 abuts against a seat portion 103 provided in a ventilation path connected to a canister. In this abutted state, such ventilation path is blocked. (See Patent Document 1)
However, as for such a control valve, firstly, although the valve member 101 is supported by the projection 100a, when the float 100 ascends, if the valve member 101 inclines, the float 100 first contacts the seat portion 103 on the upper side of the tilt of the valve member 101. Then, in this case, although the lower side of the tilt of the valve member 101 is eventually raised and the posture of the valve member 101 is corrected, this correction is accomplished by contacting an inner face of the projection 101a positioned on the lower side of the tilt of the valve member 101 and a marginal portion 100b of an upper head portion of the float 100 far from the center of the float 100. As a result, in this case (FIG. 16), a force required for completely contacting the valve member 101 with the seat portion 103 excessively increases.
Also, secondly, if the liquid level descends from a state wherein the ventilation path is blocked, the float 100 descends, and at this time, the marginal portion of the upper head portion of the float 100 is caught by the projection 101a of the valve member 101. Accordingly, the valve member 101 is pulled away from the seat portion. However, if a force for sticking to the seat portion 103 is acted on the valve member 101, such as that the inside of the fuel tank has a high pressure, and the like, it was difficult for the valve member 101 to be immediately pulled away from the seat portion 103 due to the descent of the float 100, and for the ventilation path to be unblocked responsively when the liquid level descended.
Patent Document 1: Japanese Unexamined Patent Application Publication No. H07-279789